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Background/Introduction

Retinoblastoma is a malignant tumor, which arises from the retina. The disease is particularly common in the pediatric population with up to 25% of cases presenting with bilateral disease.

Bilateral retinoblastoma is associated with a germline mutation in the RB gene and poses an exceptionally difficult dilemma for the treating physician with regard to visual preservation. The population of children carrying this mutation, and developing bilateral retinoblastoma, has also been shown to at very high risk for second malignancies with up to 50% of the population presenting with a new cancer by the age of 50 years old.

High risk patients have been shown to have poor disease-related outcomes, with 20-30% of tumors controlled in historic publications.

External beam radiation therapy remains an integral component of the treatment of refractory retinoblastoma, but is generally not employed outside of the salvage setting. Up front treatment most often consists of chemotherapy, localized radiotherapy using plaques, laser ablation, and/or enucleation.

Although dosimetric studies have suggested a potential advantage of proton beam therapy, no clinical testing has evaluated external beam radiation therapy with respect to proton therapy

The goal of the majority of new pediatric cancer protocols are aimed at diminishing both acute side effects as well as long term sequelae. With respect to the treatment retinoblastoma specifically, external beam radiation therapy can result in bony growth abnormalities, visual impairment, endocrinopathies, and secondary malignancies.

Field arrangements were heterogeneous as patients were treated at 2 institutions. Possible beam arrangements included single lateral field, single AP field, AP and lateral fields, and oblique and AP fields.

Median follow up was 17.8 months; 100% overall survival

Local control was 47% overall; in the 16 intact eyes, 6 of 16 (38%) had local control.

Of the 10 eyes with progressive local disease after proton therapy, 5 underwent salvage enucleation

Toxicity included 3 patients with cataracts and 2 patient with retinal vasculopathies

Of the 16 intact eyes treated with proton therapy, useful vision was maintained in 8 patients.

Authors' conclusions

In the authors' sample size, local control was comparable to high risk disease found in previous historic publications.

Further follow up is required to evaluate the delayed side effects of proton therapy.

Clinical/Scientific Implications

Bilateral pediatric retinoblastoma represents a tumor that may be devastating to quality of life in children.

This scenario presents a very difficult challenge for the treating physician with organ preservation paramount if possible.

In the small cohort of patients presented here, delivery of proton beam radiotherapy for treatment of pediatric retinoblastoma appears to be feasible with crude local control near 50%. Information on late effects associated with this treatment remains unavailable and will certainly contribute to the literature when longer follow-up permits analysis of quality of life following proton beam radiotherapy as opposed to photon-based treatment delivery.

Proton therapy may offer a practical solution in the prevention of bilateral enucleation. Further understanding of the risk-benefit ratio of proton therapy in this specific clinical setting may elucidate a role for proton therapy during initial treatment of advanced retinoblastoma rather than the salvage setting alone; however, further long-term data will be essential for appropriate assessment of this ratio.

Certainly, prospective randomized trials are needed to further evaluate the role of proton therapy in pediatric retinoblastoma

Mar 3, 2015 - The risk of death from prostate cancer is lower for patients treated with brachytherapy supplemented by external-beam radiation therapy and androgen suppression therapy than it is for those treated with brachytherapy alone, according to a study published online July 13 in the Journal of Clinical Oncology.